Until I get Sentinel/Vanguard, I just want to have some extreme melee fun, lol.
The trick to Soldier Melee, is Fortification Purging.
For those of you lurking/tuning in/don't understand, that means that you when you start the game, you Hit the "Ability" button (Y, Triangle... KEY...something...). The next time you hit it, you've 'purged' your 'armor', and now it's on cooldown.
THAT'S when you get the Melee buffs from Fortification.
Since we're gonna purge Fort. so often, we want to bring ONE weapon. I recommend a shotgun, probably a Disciple, barring that, the Katana. Reason being, they're both light, and you can attach the Blade to it. Increasing more melee damage. Just remember that your Heavy Melee isn't affected by the Blade.
It should be obvious that in Fortification, you go Melee Damage.
Rage, you do nothing but MeleeDamage/MartialArtist/PureRage
I'd skip Carnage personally for this build. Going grenades gives you a quick option that has no cooldown. Since your popping Fort. a lot, you can still throw your grenades while on cooldown. Grenades I'd go in any direction really. But TAKE the armor debuff at the end. If you take Radius, in slot one, go damage in two. If you want to do a ton of damage, go Damage/Damage/ArmorDamage.
For the Krogan Berserker, I'd go Weapon, Power Damage, Shotgun. You CAN go capacity, but it's not necessary. The weapon upgrade helps your shotgun, the Power Damage helps your grenades. So taking PowerCapacity will help, but your hurt your shotgun, which, in a pinch, you need.
This build will dominate Bronze (at least it should). Silver is the limit I would take this into. Gold is death trap. It's doable, but you're lacking durability.